Generally, a semiconductor device fabricating process uses photolithography for forming a resist pattern on the surface of a substrate to be processed, such as a semiconductor wafer or a LCD substrate. Photolithography includes a resist film forming process for forming a resist film on a surface of a substrate, an exposure process for transferring a circuit pattern to the resist film by exposing the resist film, and a developing process for processing the exposed resist film formed on the substrate with a developer.
The resist film forming process drops a solvent capable of dissolving a resist on the surface of a rotating substrate to form a solvent film and drops a resist solution on the surface of the substrate to form a resist film on the surface of the substrate. Different types of resist solutions meeting the purpose are used to form a plurality of resist films in layers.
Referring to FIGS. 11 and 12, a conventional resist film forming apparatus includes a spin chuck 50 capable of holding a substrate, such as a semiconductor wafer W (hereinafter referred to simply as “wafer W”) and of rotating, ten processing liquid pouring nozzles 60A for pouring resist solutions, namely, processing liquids, onto a surface of the wafer W held on the spin chuck 50, a solvent bath 70A holding the processing liquid pouring nozzles 60A at their home positions at intervals in a row beside the spin chuck 50, and a nozzle-carrying arm 80A for detachably gripping desired one of the processing liquid pouring nozzles 60a held on the solvent bath 70A to a position above the wafer W. The nozzle-carrying arm 80A holds a solvent pouring nozzle 81 for dropping a solvent capable of dissolving a resist on the wafer W. A space extending around and under the spin chuck 50 and the wafer W held on the spin chuck 50 are surrounded by a cup 23 consisting of an outer cup 23a and an inner cup 23b. Mist of the resist solution splashed about by the wafer W during the resist film forming processis caught by the cup 23. A nozzle rest 91 is disposed opposite to the solvent bath 70A. A rinsing liquid pouring nozzle 90 rests on the nozzle rest 91.
In the substrate processing apparatus thus constructed, each of the processing liquid pouring nozzles 60A is connected to a resist solution tank 62 by a flexible supply tube 61A. The supply tube 61A has a length sufficient for the processing liquid pouring nozzle 60A to move between the home position on the solvent bath 70A and a working position above the center C of the spin chuck 50. When the processing liquid pouring nozzle 60A is held at the home position, the supply tube 61 is curved upward convexly as shown in FIG. 12. A pump 63A and a filter 64 are placed in the supply tube 61A. The pump 63A pumps the resist solution to pour a predetermined quantity of the resist solution. The solvent pouring nozzle 81 is connected to a solvent tank 82 by a flexible solvent supply tube 81A. A solvent contained in the solvent tank 82 is supplied by pressure to the solvent pouring nozzle 81 by the pressure of N2 gas supplied into the solvent tank 82. As shown in FIG. 11 or 12, each of the supply tube 61A has one end connected to the processing liquid pouring nozzle 60A and the other end fixed to a resist solution tank 62. As shown in FIG. 12, the processing liquid pouring nozzle 60A carried to a working position above the wafer W by the nozzle-carrying arm 80A is connected to the resist solution tank 62 by the supply tube 61A.
Referring to FIG. 11, the nozzle-carrying arm 80A is capable of moving only in lateral directions along a Y-axis in a horizontal plane. When the desired processing liquid pouring nozzle 60A needs to be carried to the working position above the wafer W by the nozzle-carrying arm 80A, the solvent bath 70A is moved longitudinally along an X-axis, i.e., in a vertical direction as viewed in FIG. 11, to position the desired processing liquid pouring nozzle 60A at a position where the desired processing liquid pouring nozzle 60A can be gripped by the nozzle-carrying arm 80A, and then, the nozzle-carrying arm 80A is moved laterally along the Y-axis to grip the processing liquid pouring nozzle 60A.
In this conventional substrate processing apparatus, the processing liquid pouring nozzles 60A arranged in a straight row are held by the solvent bath 70A. Therefore, the supply tubes 61A connected to the adjacent processing liquid pouring nozzle 60A interfere with the supply tube 61A connected to the processing liquid pouring nozzle 60A disposed at the end of the row when the processing liquid pouring nozzle 60A disposed at the end of the row is used. Consequently, the movement of the processing liquid pouring nozzle 60A is obstructed and the other processing liquid pouring nozzles 60A are dislocated. When the processing liquid pouring nozzle 60A is located, the same processing liquid pouring nozzle 60A cannot be accurately positioned at the working position and, consequently, processing accuracy is deteriorated and the yield of the process is reduced.
If the dislocated processing liquid pouring nozzle 60A is carried to the working position and is returned to the home position on the solvent bath 70A by the nozzle-carrying arm 80A, it is possible that the resist remaining in the mouth of the processing liquid pouring nozzle 60A dries up because the processing liquid pouring nozzle 60A is held at a wrong position. When an ArF resist, which is apt to dry up, is used, scrupulous care must be taken to prevent the resist from drying.
Since the nozzle-carrying arm 80A is able to move only laterally along the Y-axis in a horizontal plane, the nozzle-carrying arm 80A cannot be accurately positioned at a gripping position where the nozzle-carrying arm 80A grips the processing liquid pouring nozzle 60A and, consequently, the nozzle-carrying arm 80A holds the processing liquid pouring nozzle 60A in an inclined position in some cases. If the processing liquid pouring nozzle 60A is dislocated, the processing liquid pouring nozzle 60A cannot be accurately positioned at the working position, processing accuracy is deteriorated and the yield of the process is reduced.